/*
Copyright (c) 2011 McDowell

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
 */

package demo.ws.maintainaddress.client;

import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;

/**
 * An implementation of <a href=
 * "http://java.sun.com/javase/6/docs/api/javax/xml/namespace/NamespaceContext.html"
 * > NamespaceContext </a>. Instances are immutable.
 * 
 * @author McDowell
 */
public final class NamespaceContextMap implements NamespaceContext {

  private final Map<String, String> prefixMap;
  private final Map<String, Set<String>> nsMap;

  /**
   * Constructor that takes a map of XML prefix-namespaceURI values. A defensive
   * copy is made of the map. An IllegalArgumentException will be thrown if the
   * map attempts to remap the standard prefixes defined in the NamespaceContext
   * contract.
   * 
   * @param prefixMappings
   *          a map of prefix:namespaceURI values
   */
  public NamespaceContextMap(Map<String, String> prefixMappings) {
    prefixMap = createPrefixMap(prefixMappings);
    nsMap = createNamespaceMap(prefixMap);
  }

  /**
   * Convenience constructor.
   * 
   * @param mappingPairs
   *          pairs of prefix-namespaceURI values
   */
  public NamespaceContextMap(String... mappingPairs) {
    this(toMap(mappingPairs));
  }

  private static Map<String, String> toMap(String... mappingPairs) {
    Map<String, String> prefixMappings =
        new HashMap<String, String>(mappingPairs.length / 2);
    for (int i = 0; i < mappingPairs.length; i++) {
      prefixMappings.put(mappingPairs[i], mappingPairs[++i]);
    }
    return prefixMappings;
  }

  private Map<String, String> createPrefixMap(Map<String, String> prefixMappings) {
    Map<String, String> prefixMap = new HashMap<String, String>(prefixMappings);
    addConstant(prefixMap, XMLConstants.XML_NS_PREFIX, XMLConstants.XML_NS_URI);
    addConstant(prefixMap, XMLConstants.XMLNS_ATTRIBUTE,
        XMLConstants.XMLNS_ATTRIBUTE_NS_URI);
    return Collections.unmodifiableMap(prefixMap);
  }

  private void addConstant(Map<String, String> prefixMap, String prefix,
      String nsURI) {
    String previous = prefixMap.put(prefix, nsURI);
    if (previous != null && !previous.equals(nsURI)) {
      throw new IllegalArgumentException(prefix + " -> " + previous
          + "; see NamespaceContext contract");
    }
  }

  private Map<String, Set<String>> createNamespaceMap(
      Map<String, String> prefixMap) {
    Map<String, Set<String>> nsMap = new HashMap<String, Set<String>>();
    for (Map.Entry<String, String> entry : prefixMap.entrySet()) {
      String nsURI = entry.getValue();
      Set<String> prefixes = nsMap.get(nsURI);
      if (prefixes == null) {
        prefixes = new HashSet<String>();
        nsMap.put(nsURI, prefixes);
      }
      prefixes.add(entry.getKey());
    }
    for (Map.Entry<String, Set<String>> entry : nsMap.entrySet()) {
      Set<String> readOnly = Collections.unmodifiableSet(entry.getValue());
      entry.setValue(readOnly);
    }
    return nsMap;
  }

  @Override
  public String getNamespaceURI(String prefix) {
    checkNotNull(prefix);
    String nsURI = prefixMap.get(prefix);
    return nsURI == null ? XMLConstants.NULL_NS_URI : nsURI;
  }

  @Override
  public String getPrefix(String namespaceURI) {
    checkNotNull(namespaceURI);
    Set<String> set = nsMap.get(namespaceURI);
    return set == null ? null : set.iterator()
        .next();
  }

  @Override
  public Iterator<String> getPrefixes(String namespaceURI) {
    checkNotNull(namespaceURI);
    Set<String> set = nsMap.get(namespaceURI);
    return set.iterator();
  }

  private void checkNotNull(String value) {
    if (value == null) {
      throw new IllegalArgumentException("null");
    }
  }

  /**
   * @return an unmodifiable map of the mappings in the form prefix-namespaceURI
   */
  public Map<String, String> getMap() {
    return prefixMap;
  }

}
